Bifocal lens.



E. J. lPINK.

BIFOGAL LENS.

APPLICATION PILED Nov. 16, 1910.

Patented Nv. 24, 1914.-

I I mm FFIUE.

EDWARD J. FINK, OlFvS-YCAMORE, ILLINOIS.

BIFOCAL LENS.

Lunario.

Specification of Letters Patent.

Patented Nov. 2d, 1914i.

Application filed November 16, 1910. Serial No. 592,687.

`State of Illinois, have invented certain new and useful Improvements inBifocal Lenses, of which the following is a specification.

My invention relates to bi-focal lenses and to the method of making suchlenses, and has for its object to produce a bi-focal lens, preferably ina single piece which shall have both the distance and reading fieldsrelatively large and so arranged with reference toeach other than theuser shall not only be inconvenienced as little as possible by the.presence of the two lenses in the same structure but shall have a lens,the reading field or portion of which in no way interrupts or projectsinto the distance field, which is itself of oblong shape and correspondsto the normal field of distance vision.

Referring to the drawings, Figure 1 shows a plan, side and end View ofan ordinary lens blank; Fig. 2 shows a plan and sectional side and endview of the blank after the first grinding operation; Fig. 3 shows aplan and sectional side and end view of the blank after the secondgrinding operation; Fig. 4 shows a plan and sectionaly side and end Viewof the blank after the concave side of the lens has been ground; Fig. 5is a plan view of the lens, some of the various shapes which the readingfield may take being indicated in dotted lines; Fig. 6 is a diagramshowing the convex surface of the lens after that surface has beenground, the radii of curvature of the several surfaces of a specificexample being indicated on the axes of 90 and 180. Fig. 7 is a similarView of the concave surface of the lens similarly marked; Fig. 8 is asimilar diagram showing th'e resulting optical effect-of the combinationof the convex and concave surfaces shown in Figs. 6 and 7, and Figs. 9,10 and 11 show various forms which may be given to the reading field.

In producing my bi-focal lens, a lens blank A as shown in Fig. 1 is Arstsubjected to a grinding action to simultaneously produce thereongenerated surfaces whose radii in planes at right angles to each otherare or may be different. Thus the curve 1 which may be taken as alongthe4 90 axis of the lens may be .of +7 .5 diopters, while the curve 2which may be taken as along the 180 axis may be of dioptersl Thesoground blank is then subjected to a second grinding to produce thereonsurfaces of curvature suitable for the distance field of the lens; asfor example a surface 3. along the 90 axis having a power of +6 dioptersand a surface 4c along the axis ofA 180 as of +4.?) diopters. As theresult of these two grindings there isl produced a bi-focal lens havingan elliptical, oval, or oblong distance field, surrounded by an areahaving a suitable curvature fortlie reading field. rl`he lens may thenbe completed by grinding the reverse side concavely to produce surfaceshaving along the 90 axis, a power of, say, 5.0 diopters, and a poweralong the 180 axis, say, of 8.5 diopters.

The resulting lens will as shown in Figs. 4 and 8 have an oblongdistance field having the optical power due to a curved surface of +1.0diopter alongboth axes, this distance field being surrounded by areading field having `a power of;l+2.5 diopters on both axes.

It is to be understood that the specific example here given is intendedfor illustration only, as it is obvious that these curves may be variedto produce distance and reading fields of any desired curvature, and itis this feature' which constitutes one of the great advantages of myinvention, viz., that in a bi-focal lens both reading and distanceportions may each be not only such as to independently correct for nearor far sightedness, but may also be curved to independently prov-ide forthe correction of astigmatism or decentered to provide for prismaticcorrection.

The distance or reading field may be decentered for purposes ofprismatic correci tion by properly inclining or tilting the lensblanksupport with reference to the grinding tool and such decentering may beapplied with equal facility to eitherl the distance or reading fieldindependently of each other.

The `above described compounding ofthe optical effect of the differentsurfaces is diagrammatically illustrated in Figs. 6. 7 and 8, the poweralong the 90 and 180 axes, in diopters being marked.

As will appear from Fig; 6, the distance field is a surface of compoundcurvature resulting from a simultaneously grinding' on two Y cylindricalsurfaces of respectively +45 .diopters (160 axis) and +6 diopters (940"anis); whilethe reading field is the ico . noted that icy my method ofohlonej distance field is provhich prov .es lor the normal extent ordistance ion and that with such oblong distance licld is associated areading' field which nav extend along; the whole edge of the distancefield, so that in neither distance nor near seeing is there any lateralintrusion or roentrance olf one field into the other.

t l() and ll, D indicates the diseld and l the reading field. The anceiichl has hee shown in the various nes as surrounded hy a dotted line,but acti* .l lens, this line is practically invisible.

ln the above described example, the concave side oi3 the lens has heenshoivn as a surface oli double curvature7 but ult desired may he equallvcilected oy 'ngi' a. simple cylindrical surface; thus it "lace il lic of+7.15 diopters and surface f2v +115 diopters7 and surface 23 oi? +6,'cxiiters and suriace 1i o +1.() diopter, the concave side. ot the lensmay oe ground as a plain r.\fliii ler having a power of 5.0 diopters onthe 90 axis. the line of section on the 190 axis being, course, astraight line.

'i he resulting' lens would have an oblong; distance field having; theoptical power duc to a curved surface of +1.() diopter heth axes7 and areading licld 'having power oi diopters along both axes. "lther inodcsof combining the curvatures et the tivo surfaces will readily-7 suggestthemselves to those familiar ivith the art.

'The curvatures, as shown in tle drawings. ha heen distorted to moreclearly indicate thi` relations o if the sui-'faces to each other.

.l claim: l. la lil-'local lens ground from a single piece i" glasshaving an uninterrupted ololongr distance iicld and a reading iieldelvtending along` one edge ci the distance held, the surfaces otdill'crent curvature merging into cach other Without abrupt angles.

oueogiece lai-'focal lens ground 'from a single piece of glass having annnintere :long distance lield and a readinfr e c. .g alone praetically7the length ol one -lpc of the distance field. the surfaces .ai rasee ofdifferent curvature merging" into cach other Without abrupt angles.

3. il. one-piece loi-focal lens ground from a single piece of glasshaving an uninter rupted oblong distance field and a reading fieldextending along one edge of the distance ield, the surfaces of diierentcurva ture merging into each other Without abrupt angles.

1. A one-piece loi-focal lens ground from a single piece o glass havingan. uninterrupted oblong distance field and a reading field extendingalong practicalli7 the length. of one edge of the distance field. thesuri'aces of dilerent curvature merging into each other without abruptangles.

5. A loi-coal lens having a convex face made up of a distance field anda reading field, each held having a surface of different dioptriccurvature along planes at an angle to each other.

(i. A loi-focal lens having a convex face made up of a distance-field`and a reading eld. cach field having a surface of different dioptriccurvature along planes perpendicular to the plane oi.E the lens atanangle to each other, and a concave tace.

7. A lui-focal lens having a convex face made up of a distance field anda reading eld. each held having a surface oit ditiferent dioptriccurvature along planes perpendicular to the plane of the lens at anangle to each other, and a concave face, the curvatures of the convexand concave surfaces heine; so proportioned that distance and readingelds have the desired power for the area oit' their respective heide.

8. A loi-focallens ground from a single piece of glass Whose readingsfield does .not reenter into the distance eld, the surfaces of dillerentcurv-.iture merging into each other without abrupt angles. A

9.. A one-piece lai-focal lens ground from a single piece ot glass Whosedistance field is oval.y and Whose reading field does not reenter intoits oval distance field. the surfaces oi different curvature merginginto each other Without abrupt angles.

10. The process ot'. making loi-focal lenses, which consists insimultaneously grinding a blank to produce a convex surface having inplanes at an angle to each other different dioptric radii. then furthergrinding the blank to produce thereon a second convex surface havingA inplanes at auf angle to each other dioptric radii differing' lfrom eachother and ot lengths different from the cor. responding radii of theirst surface.

1l. The process ot making hi-focal lenses, which consists insimultaneously grinding a hlank to produce a convex surface. having inplanes atan angle to each other different dioptric radii, and thenfurther grinding tleel'iianh to produce thereon a second con ver;sui-.Face having in planes aft-@an angle rio each other differentdioptrie radii of greater length than the corresponding radii of theiirst surface, thereby producing an oblong distance field surrounded bya reading eld, and then grinding the reverse side of the blank to form aconcave surface.

l2. IThe process of making bi-focal lenses, which consists insimultaneously grinding a blank 'to produce a convex surface having inplanes at an angle to each other dierent dioptric radii, then furthergrinding the blank to produce thereon a second convex surface having inplanes at an angle to each other different dioptric radii of greaterlength than the corresponding radii of the first surface, therebyproducing an oblong distance iield surrounded by a readino field..

13. The process of making bi-focal lenses, which consists insimultaneously grinding a blank to produce a convex surface having inplanes at an angle to each other diierent dioptric radii, then furthergrinding the blank to produce thereon a second convex surface having inplanes at an angle to each other different dioptric radii of greaterlength than the corresponding radii of the rst surface, therebyproducing an oblong Copiez of this patent may be obtained for distancefield surrounded by a reading field,

and then grinding the reverse side of the blank to Aiform a concavesurface.

lil, The process of making oi-focal lenses, which consists insimultaneously grinding a blank to produce a convex surface having inplanes at an angle to each other diierent dioptric radii, then furthergrinding the blank to produce thereon a second convex surface having inplanes at an angle to each other dierent dioptric radii of greaterlength than the corresponding radii of the rst surface, 'therebyproducing an oblong distance field surrounded by a reading field, andthen grinding the reverse side of the blank to form a concave surface,the curva- Ntures of the concaveand convex surfaces being soproportioned that the distance and reading fields have the desired powerover the area of their respective fields.

ln testimony whereof, I aflix my signature in presence of two Witnesses.Y

vc cents each, by addressing the Gommissioner of Patents Washington, 1LC.

